HBV infection remains a major public health problem, affecting approximately 2 billion people worldwide. Among them, 350 million people worldwide and 1.4 million in the US develop a chronic infection, which can lead to chronic persistent hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). Every year 500,000 to 1 million people die from the end stage of liver diseases caused by HBV infection.
Despite the availability of a prophylactic HBV vaccine, the burden of chronic HBV infection continues to be a significant unmet worldwide medical problem, due to suboptimal treatment options and sustained rates of new infections in most parts of the developing world. Current treatments do not provide a cure and are limited to only two classes of agents (interferon and nucleoside analogues/inhibitors of the viral polymerase); drug resistance, low efficacy, and tolerability issues limit their impact. The low cure rates of HBV are attributed at least in part to the presence and persistence of covalently closed circular DNA (cccDNA) in the nucleus of infected hepatocytes. However, persistent suppression of HBV DNA slows liver disease progression and helps to prevent HCC. Current therapy goals for HBV-infected patients are directed to reducing serum HBV DNA to low or undetectable levels, and to ultimately reducing or preventing the development of cirrhosis and HCC.
The HBV is an enveloped, partially double-stranded DNA (dsDNA) virus of the hepadnavirus family (Hepadnaviridae). HBV capsid or core protein (CP) plays essential roles in HBV replication. The predominant biological function of capsid protein is to act as a structural protein to encapsidate pre-genomic RNA and form immature capsid particles, which spontaneously self-assemble from many copies of core dimers in the cytoplasm. Capsid protein also regulates viral DNA synthesis through different phosphorylation status of its C-terminal phosphorylation sites. Also, capsid protein might facilitate the nuclear translocation of viral relaxed circular genome by means of the nuclear localization signals located in the Arginine-rich domain of the C-terminal region of capsid protein. In the nucleus, as a component of viral cccDNA minichromosome, capsid protein could play a structural and regulatory role in the functionality of cccDNA minichromosomes. Capsid protein also interacts with viral large envelope protein in endoplasmic reticulum (ER) and triggers the release of intact viral particles from hepatocytes.
Capsid related anti-HBV inhibitors have been reported. For example, phenylpropenamide derivatives, including compounds named AT-61 and AT-130 (Feld J. et al. Antiviral Res. 2007, 76, 168), and a class of thiazolidin-4-ones from Valeant (WO2006/033995), have been shown to inhibit pregenomic RNA (pgRNA) packaging. Heteroaryldihydropyrimidines or HAPs were discovered in a tissue culture-based screening (Weber et al., Antiviral Res. 2002, 54, 69). These HAP analogs act as synthetic allosteric activators and are able to induce aberrant capsid formation that leads to degradation of the core protein. A subclass of sulphamoylarylamides shows activity against HBV (WO2013/006394, WO2013/096744, and WO2014/184365). It was also shown that the small molecule bis-ANS acts as a molecular ‘wedge’ and interferes with normal capsid-protein geometry and capsid formation (Zlotnick A. et al. J. Virol. 2002, 4848).
There is a need in the art for novel therapeutic agents that treat, ameliorate or prevent HBV infection. Administration of these therapeutic agents to an HBV infected patient, either as monotherapy or in combination with other HBV treatments or ancillary treatments, will lead to significantly improved prognosis, diminished progression of the disease, and enhanced seroconversion rates.